Nice looking Slant 6 car! Price is a little high for a /6 car unless the paint and frame are perfect. I have no idea how Hawaii location impacts price?
These cars have the typical problem areas: floor boards, truck floor, rocker panels, wheel wells, lower fenders - check those areas carefully for rust. The front of the frame also is an area to inspect carefully. Ask when it was most recently painted and if there are pictures of the body work during paint.
Engine looks to have been reworked at some point. The block, valve cover, and air cleaner have been painted non-stock colors. I'd try to find out about details of any engine rebuild.
Disk brakes would increase value, as would electronic ignition - those are upgrades you might want to make if you purchased the car.
Be advised that it probably has small bolt pattern wheels (5 x 4") which will limit your wheel and tires choices if don't like what is on the car now.
